Method and device for biological treatment of water in swimming pools

ABSTRACT

The invention relates to a method for biological treatment of water in swimming pools. The method requires neither chlorine nor other toxic chemicals in the pool water, since near-surface pool water is mechanically purified in a first water circuit and suspended matter situated in the pool water is first retained in a biological filter ( 9 ) in a second water circuit and organic matter contained in said suspended matter, such as algae or detritus, and also organic matter dissolved in the pool water, are mineralized by the action of bacteria, wherein the phosphorus contained in the organic matter is catabolyzed to form dissolved reactive phosphate that is then bound by adsorption in an anion exchanger ( 14 ).

The invention relates to a method and a device for biological treatmentof water in swimming pools.

In the conventional purification of water in swimming pools, the poolwater is passed out via a bottom outlet and a skimmer or, if present, asurface channel, and mechanically purified in a filter, in particular asand filter. In addition it is necessary to add disinfectant, forexample chlorine, to the pool water, in order to prevent themultiplication of pathogens and algae.

In what are termed natural swimming ponds, the water treatment proceedsprincipally with the aid of water plants and/or biological filters.Natural swimming ponds are therefore enjoying increasing popularity. Acertain disadvantage of natural swimming ponds is, however, that theirarea requirement is relatively high, since the planted treatment zonetakes up a proportion of 25% to 75% of the water area. Furthermore,unsightly algal blooms can occur in natural swimming ponds. Some usersof natural swimming ponds consider it to be a further disadvantage thatin such a near-natural habitat, organisms such as water insects oramphibians rapidly colonize.

The object underlying the invention is to provide a method and a devicefor treating the pool water for swimming pools, which method requiresneither chlorine nor other toxic chemicals in the pool water and doesnot have the disadvantages mentioned of natural swimming ponds.

As far as the method is concerned, the object in question is achievedaccording to the invention in that near-surface pool water ismechanically purified in a first water circuit and in that suspendedmatter situated in the pool water is first retained in a biologicalfilter in a second water circuit and organic matter contained in saidsuspended matter, such as algae or detritus, and also organic matterdissolved in the pool water, are mineralized by the action of bacteria,wherein the phosphorus contained in the organic matter is catabolyzed toform dissolved reactive phosphate that is then bound by adsorption in ananion exchanger.

The system according to the invention is characterized in that a firstpump-operated water circuit is provided for near-surface pool waterhaving a mechanical filter appliance and a second, also pump-operated,water circuit is provided having a biological filter and an anionexchanger arranged downstream of the latter.

The invention therefore makes possible the operation of a swimming poolwithout the use of chlorine or other disinfectants. In the one watercircuit, the mechanical purification of near-surface pool waterproceeds, and in the second water circuit, in a biological filter,retention of suspended matter and mineralization of organic mattersituated in the pool water proceed, wherein the phosphorus contained inthe organic matter is catabolyzed to form dissolved phosphate that isthen bound by adsorption in an anion exchanger. The growth of algae inthe pool water is thereby largely prevented by phosphorus limitation, byanalogy with natural lakes.

The mechanical purification of the near-surface pool water and theimplementation of the associated water circuit are possible in a varietyof ways. A particularly simple and at the same time very effectivemeasure is to filter the near-surface pool water through a sieve, inparticular a bow screen sieve. Sieves reliably retain impurities and maybe easily cleaned.

Each water circuit is operated by a separate pump which, with respect toits power, is geared to the requirements of the respective watercircuit. A particular advantage of the combination of biological filterand anion exchanger in the second water circuit is that both filtersrequire only a relatively low through-flow, and so a single pump issufficient for operating this circuit and intermediate storage of poolwater is not required.

In one embodiment of the invention, the biological filter is afine-grained filter material, in particular sand or porous material,having bacteria colonized thereon. The biological filter may thereby beconstructed in an expedient and inexpensive manner, and any cleaningthat is necessary or replacements are possible without problems.

In a further preferred embodiment of the invention, the anion exchangeris accommodated in a container that is let into the ground. The anionexchanger can therefore be positioned in a readily accessible and at thesame time visually inconspicuous manner for maintenance work. Connectiontubes that are required in the circuits are preferably laid belowground.

The biological filter can likewise be arranged inconspicuously and inparticular close to the swimming pool. It is expedient, for example, toarrange the biological filter below a wooden bridge or the like or belowground with a detachable covering.

The pumps present in both water circuits can be accommodated in anexpedient and simple manner in a joint pump shaft that is let into theground.

Further features, advantages and details of the invention will now bedescribed in more detail with reference to the drawing. The singleFIGURE, FIG. 1, shows schematically one variant embodiment of a deviceaccording to the invention.

FIG. 1 shows a swimming pool 1, which can be constructed in aconventional manner, for example as a concrete pool having a filmcladding. For purifying the water in the swimming pool 1, two separatewater circuits are provided that are operated simultaneously.

The one water circuit serves for mechanical purification or filtrationof the near-surface swimming pool water. This circuit, in the embodimentof the invention shown, comprises a skimmer 2 that is connected to theswimming pool 1 close to the water surface, which skimmer, in theembodiment shown, has a feed 2 a having a freely pivotable skimmer flap2 b, a skimmer housing 2 c, and also an outlet 2 d in the bottom regionthereof. In the housing 2 c, a sieve, for example a bow screen sieve 3,is accommodated for filtering the swimming pool water. A pipe 4 laid inthe ground connects the outlet 2 d of the skimmer 2 to a pump 5 which isaccommodated in a separate pump shaft 6 that is let into the ground. Viaa further pipe 7 that is laid in the ground, the water is pumped backinto the swimming pool 1. In this water circuit, water is thereforetaken off from the water surface by suction and mechanically purifiedfrom particles, suspended materials and the like in a filter or sieve 3.Purified water can be fed to the pool interior via inflow nozzles, in amanner that is not shown. If a surface channel is laid around theswimming pool 1, the water can be drawn from this channel by suctioninto a container/shaft in which there is a sieve/filter. For this watercircuit, the use of a relatively powerful pump 5 is advantageous. Inorder to save electrical energy, the pump 5 is preferably only operatedfor a few hours per day.

In the second water circuit, in the swimming pool water, in a similarmanner to natural lakes, the growth of algae is limited or substantiallyprevented by phosphorus limitation. For this purpose, the pool water istreated in the second water circuit in two steps. The pool water passesthrough an outlet 8 provided in the pool wall, preferably directly, intoa biological filter 9. The biological filter 9 consists of a flatcontainer 9 a that is let into the ground and which is packed up to acertain height with a fine-grained, inert filter material 9 b,preferably sand or porous materials such as expanded clay or lava rock.The pool water that is drawn in by suction via a second pump 12 that ispositioned in the pump shaft 6 percolates through the filter material 9b, wherein suspended matter (these are the particulate impurities), suchas algae, detritus and suspended materials, are filtered out. The filter9 therefore acts as a mechanical filter by retaining the suspendedmatter. The biological filter action of the filter material 9 b is basedon the activity of bacteria. The bacteria develop spontaneously, form abiological lawn on the grain surfaces of the filter material and adapt,with some time delay, to the water loading that occurs.

The suspended matter in the pool water originates from introductionsfrom the environment such as leaves, dust, insects, and from impuritiesintroduced by use, for example skin residues, and also from the organicsubstances formed such as algae. The pool water in addition containsdissolved organic matter as impurities. The suspended matter, asmentioned, is retained in the filter 9, organic matter—dissolved andparticulate—is mineralized by the bacteria which has colonized in thefilter material. The phosphorus that is contained in this organic matteris catabolyzed to form dissolved phosphate, substantially orthophosphate(PO₄ ³⁻). The filtered percolated pool water leaves the biologicalfilter 9 at the bottom of the container 9 a via an outlet 10 to which apipe 11 is connected that leads to the pump 12. The pump 12 pumps thepool water that is filtered in the biological filter 9 to a container 14a that is likewise let into the ground and which contains an anionexchanger 14. The anion exchanger 14 binds, by adsorption, the negativeions from the pool water, in particular and preferably PO₄ ³⁻, but alsonitrite (NO₂ ⁻) and nitrate (NO₂ ⁻). The phosphorus concentration in thepool water is reduced in this method to a very low value, in particularto less than 10 μg/l, as a result of which primary production of algaeor algal growth is substantially prevented in the pool water. The pump12 conveying pool water through the anion exchanger 14 has only arelatively low power and runs permanently. A circulation time for all ofthe pool water of the order of magnitude of two days has proved to besufficient. Therefore, the volume and the area of the biological filter9 can also be kept relatively small, and so the filter container 9 a canreadily be accommodated, for example, below a wooden bridge 15. Thebiological filter 9 is in addition provided with a light-impermeablecover, and so no unwanted algae can colonize it. An arrangement of thebiological filter 9 below ground is also possible.

Since the pool water is well purified from suspended matter in thebiological filter 9, the downstream anion exchanger 14 only needs to bebackwashed rarely. The anion exchanger 14 is replaced after a certainoperating time, as soon as it is saturated with phosphate.

A particular advantage of the combination of biological filter 9 andanion exchanger 14 is that both filters require only a relatively lowthrough-flow, the biological filter 9 in order that the biologicalmethods proceed optimally and the biological lawn is not floated off,and the anion exchanger 14, because a certain contact time is necessaryfor the adsorption. Therefore, both components 9, 14 can be charged withthe same hydraulic through-flow.

For cleaning the pool bottom and the pool walls, a conventional poolrobot can be used which is operated at relatively short intervals, forexample daily. By using a robot, the growth of filamentous algae on thepool walls can be effectively prevented.

By taking samples, in particular of water in the pool, from the outletof the anion exchanger and immediately downstream of the biologicalfilter, the phosphorus concentration, the pH, the oxygen concentrationand other parameters can be continuously monitored.

The invention is not restricted to the embodiment(s) shown anddescribed. Other skimmer types than that described can be used. Thebiological filter can also be constructed as a trickling filter ormicrofiber filter.

LIST OF REFERENCE NUMBERS

-   1 . . . Swimming pool-   2 . . . Skimmer-   2 a . . . Feed-   2 b . . . Skimmer flap-   2 c . . . Housing-   2 d . . . Outlet-   3 . . . Sieve-   4 . . . Pipe-   5 . . . Pump-   6 . . . Pump shaft-   7 . . . Pipe-   8 . . . Outlet-   9 . . . Biological filter-   9 a . . . Container-   9 b . . . Filter material-   10 . . . Outlet-   11 . . . Pipe-   12 . . . Filter pump-   14 . . . Anion filter-   14 a . . . Container-   15 . . . Wooden bridge

1. Method for biological treatment of water in swimming pools,characterized in that near-surface pool water is mechanically purifiedin a first water circuit and in that suspended matter situated in thepool water is first retained in a biological filter in a second watercircuit and organic matter contained in said suspended matter, such asalgae or detritus, and also organic matter dissolved in the pool water,are mineralized by the action of bacteria, wherein the phosphoruscontained in the organic matter is broken down to form dissolvedreactive phosphate that is then bound by adsorption in an anionexchanger.
 2. Method according to claim 1, characterized in that thenear-surface pool water is filtered through a sieve, in particular a bowscreen sieve.
 3. Method according to claim 1, characterized in that eachwater circuit is operated by a pump.
 4. Device for biological treatmentof water in swimming pools, characterized in that a first pump-operatedwater circuit is provided for near-surface pool water having amechanical filter appliance and a second, also pump-operated, watercircuit is provided having a mechanical/biological filter and an anionexchanger arranged downstream of the latter.
 5. Device according toclaim 4, characterized in that the mechanical filter appliance in thefirst water circuit has a sieve, in particular a bow screen sieve. 6.Device according to claim 4, characterized in that the biological filtercomprises a fine-grained filter material, in particular sand or porousmaterial, having bacteria colonized thereon.
 7. Device according toclaim 4, characterized in that the anion exchanger is accommodated in acontainer that is let into the ground.
 8. Device according to claim 4,characterized in that the biological filter is covered by a woodenbridge or is arranged below ground.
 9. Device according to claim 4,characterized in that the pumps present in both water circuits areaccommodated in a joint pump shaft that is let into the ground.